Paleoenvironmental and archeological significance of alluvial placers of the Brazilian Amazon
ResumoThe gold and tin-bearing alluvial placers of the Brazilian Amazon high terrains constitute a remarkable record of the environmental changes which occurred in the region during the Quaternary. The deposits are typically immature, and have been formed by mass movements under semi-arid climate. They are clearly older than the last rain forest spreading, and may be attributed to cyclic episodes which have been correlated to the Pleistocene glaciations. These interpretations are highlighted by the discovery of abundant polished stone artifacts which have been preserved within Pleistocene deposits. The archeological record allows the demarcation of an important cultural tradition, widely disseminated in the Brazilian Amazon, and gives a starting point to review our present knowledge of the Amazonian Prehistory - still centered in studies on the Várzea" region, of Holocene age. This means that the human establishment in the Amazon is much older than formerly believed.